In vitro and in vivo models will be studied to elucidate the mechanisms responsible for the interaction of oncogenic virus, thymic epithelial cells and thymic cortical cells which result in lymphoma development in the AKR mouse. Cell culture methods to induce transformation of mouse thymic cells to lymphoma cells will be developed. Cell lines from virus accelerated and spontaneous lymphomas will be established in vitro, and their virus production analyzed in detail. This will also be done for in vitro lines of thymic epithelium established from mice of various ages. BIBLIOGRAPHIC REFERENCES: Hays, E. F., Vredevoe, D. L.: A Discrepancy in XC and Oncogenicity Assays for Murine Leukemia Virus in AKR Mice. Cancer Res. 37:726-730, 1977. Beardsley, T. R., Hays, E. F.: Effects of Cell Density in Culture on Mitogen and MLC Responsiveness of AKR Thymocytes. Fed. Proc. 36:1221, 1977.